Temperable Glass Coating

ABSTRACT

The invention relates to a silver low-E coating for glass which is temperable and can be applied by means of sputter processes onto the glass. The individual layers of the coating are cost-effective standard materials. One embodiment of the invention for example is comprised of a glass substrate, an Si 3 N 4  layer disposed thereon of a thickness of approximately 15 nm, a TiO 2  layer of 15 nm thickness on the Si 3 N 4  layer, a 12.5 nm thick Ag layer on the TiO 2  layer, a NiCrO x  layer of approximately 5 nm thickness on the Ag layer and a terminating 45 nm thick Si 3 N 4  layer.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a non-provisional, and claims the benefit, ofcommonly assigned U.S. Provisional Application No. 60/893,764, filedMar. 8, 2007, entitled “Temperable Glass Coating,” the entirety of whichis herein incorporated by reference for all purposes.

BACKGROUND OF THE INVENTION

The invention relates to a temperable glass coating according to thepreamble of patent claim 1.

Coatings on transparent glass or transparent synthetic material serve toreflect or absorb specific wavelengths or wavelength ranges of incidentlight. Known are coatings on optical lenses and on window panes, alsoreferred to as architectural glass, as well as the coatings on motorvehicle window panes.

The most important function of a coating on architectural glass is thereflection of thermal radiation in order for a room not to become toowarm during the summer and not too cool during the winter. In theprocess the visible light is to be minimally weakened, i.e. the coatingshould have high transmission in the visible range (approximately 400 nmto 700 nm under daylight vision and approximately 390 nm to 650 nm undernight vision) and high reflection for thermal and infrared radiation(wavelength>700 nm).

Layer systems fulfilling this function are referred to as low-E layersystems, “E” representing emissivity (=degree of emission or emissioncapability). This is intended to express that these layer systems onlyoutput low thermal radiation from a building room to the outside.

As a rule, heat regulation is attained thereby that onto glasselectrically high-conducting layers are applied, frequently comprising ametal such as Cu, Ag, Au with a very low radiation emission coefficient.

Due to the light reflection of these low-E layers, which is often toohigh, these layers are sometimes antireflection-coated with the aid ofadditional transparent layers. By applying the transparent layers, thedesired color tint of the glass pane can also be set.

A coated substrate is already known which comprises at least onemetallic coating layer and further dielectric layers (EP 1 089 941 B1).This coated substrate is structured such that it can be tempered andbent.

A substrate provided with a multilayer system is furthermore known whichis also temperable and bendable (U.S. Pat. No. 6,576,349 B2, U.S. Pat.No. 6,686,050 B2). The multilayer system utilized herein comprises twolayers which reflect infrared radiation and which are each encompassedby two NiCrO_(x) layers.

Further, a heat-insulating layer system is known which, after thecoating, is tempered and bent (DE 198 50 023 A1 or EP 0 999 192 B1).This layer system comprises a precious metal layer disposed on a TiO₂layer, the two layers being encompassed by suboxidic NiCrO₂.

Lastly, temperable coatings are also known which utilizesubstoichiometric Si_(x)N_(y) or SiN_(x)O_(y) (WO 2005/19127 A1, WO2005/034192 A2).

The different layers are, as a rule, produced with the aid of sputterprocesses, in which by means of positive ions particles are knocked outof so-called targets, which particles are subsequently deposited on thesubstrate, which may be architectural glass.

The known layer systems entail at least one of the following citeddisadvantages:

expensive or exotic starting materials for sputter targets

complex and complicated process control

complex layer structuring

inadequate optical properties

severe changes of the essential properties of the coated glass by atemper process.

The invention addresses the problem of providing a simple andcost-effective silver low-E coating, which only minimally changes itsessential properties after tempering.

BRIEF SUMMARY OF THE INVENTION

A temperable substrate with a coating is disclosed according to oneembodiment of the invention. The temperable substrate may include aglass substrate with a first layer comprising Si_(x)N_(y)O_(z) disposedthereon. A second layer comprising TiO₂ may be disposed on the firstlayer. A third layer comprising Ag may be disposed on the second layer.A fourth layer comprising NiCrO_(k) may be disposed on the third layer.A fifth layer comprising Si_(x)N_(y)O_(z) may be disposed on the fourthlayer. The layers that include Si_(x)N_(y)O_(z), x/y≦0.75, y/z>4, and0<k<2.

A method of making the above mentioned temperable substrate is alsodisclosed. The method includes sputtering each of the layers on thesubstrate.

DETAILED DESCRIPTION OF THE INVENTION

The advantage attained with the invention comprises in particular thatonly standard target materials, such as boron-doped silicon (Si:B) ortitanium-doped silicon aluminum (SiAl:Ti) as well as titanium oxide,silver or nickel-chromium are employed.

Since pure silicon is not conductive, silicon sputter targets must bedoped, for example, with boron in order for them to be utilizable at allfor DC or MF sputtering. The additives boron, aluminum or titanium,which are also contained in the layer, do not have a negative effect.Si₃N₄ comprises only small quantities of oxygen (O_(m)) as layermaterial.

In the following the process parameters of a sputter process carried outin the production of the invented coating Si₃N₄—TiO₂—Ag—NiCrO_(x)—Si₃N₄on glass are compiled in the form of a table. The designations usedindicate the following:

KT=Cathode

sccm=standard cubic centimeter per minute (also Nml per minute;Nml=standard millimeter)

AC=alternate current

DC=direct current

V=Volt (voltage)

A=Ampere (current)

W=Watt (power)

k=1000

F=10⁻⁶

bar=0.1 MPa=10⁵ Pa (Pa=Pascal=pressure)

planar=planar cathode

rot=rotating cathode

:=doped with

KT 1, KT 2 etc. are here the different cathodes of an inline process,past which a substrate—here glass—is successively moved.

m=number greater than or equal to zero.

TABLE 1 Cathode KT 1 KT 2 KT 3 KT 4 KT 5 KT 6 KT 7 KT 8 Material GasInlet Si₃N₄ TiO₂ TiO₂ TiO₂ Ag NiCrO_(x) Si₃N₄:O_(m) Si₃N₄:O_(m) Argon700 sccm 500 sccm 450 sccm 450 sccm 590 sccm 480 sccm 1000 sccm 1000sccm Oxygen 20 sccm 293 sccm 274 sccm 265 sccm 10 sccm 40 sccm 50 sccm50 sccm Nitrogen 585 sccm 50 sccm 50 sccm 50 sccm 0 sccm 0 sccm 1070sccm 1195 sccm Process AC rot AC rot AC rot AC rot DC planar DC planarAC rot AC rot Pressure 4.91 μbar 4.22 μbar 4.36 μbar 4.15 μbar 4.34 μbar4.65 μbar 8.83 μbar 9.23 μbar Voltage 340.0 V 448.0 V 446.0 V 447.0 V408.0 V 458.0 V 265.0 V 266.0 V Current 102.0 A 223.0 A 224.0 A 225.0 A7.0 A 6.5 A 223.0 A 222.0 A Power 35.0 kW 100.0 kW 100.0 kW 100.0 kW 2.7kW 2.9 kW 59.0 kW 59.0 kW

The TiO₂ layer has here a double function as an anti-reflectingdielectric and as a seed layer or blocker for the succeeding silverlayer. Application of the TiO₂ layer as three layers (KT 2, KT 3, KT 4)takes place for the reason that at given substrate rate one cathodealone would not yield the adequate layer thickness. For the same reasonthe Si₃N₄:O_(m) layer is applied in two steps. Before tempering, none ofthe layers had a gradient. Special doping in the target material of thesputter process was omitted.

The dielectric layers—Si₃N₄ and TiO₂—are preferably sputtered fromrotating magnetrons. For the TiO₂ layer ceramic TiO_(x) target can beutilized, which can be sputtered using MF techniques (approximately 10kHz to 80 kHz) or AC techniques or also DC techniques.

The Ag layer and the NiCrO_(x) layers are typically sputtered frommetallic targets by means of DC techniques. For all processes planarand/or rotating targets are conceivable. For TiO₂ and Si₃N₄ coatingsrotating targets have preferably been used for some time. For Ag andNiCrO_(x) layers planar targets are conventionally used, howeverrotating targets are also feasible.

As is evident based on Table 1, only small quantities of oxygen arerequired in the Si₃N₄ processes. A high pressure is required in theconcluding Si₃N₄. Si₃N₄:O can generally also be written asSi_(x)N_(y)O_(z), wherein x/y≦0.75 and y/z≧4 when z≠0 applies. Themaximum oxygen flow for the NiCrO_(x) process occurs on the metal branchof the hysteresis, for which narrow apertures and a gas inlet below thisaperture in the sputter chamber are preconditions.

The right columns of Table 1 show ratios N₂:O₂≧20:1. However, the layerscan also be generated for example at a gas flow ratio of N₂:O₂=4:1. Thelayer composition does not reflect this gas flow ratio of N₂:O₂. Ratherdifferent parameters exert their influence if relatively more oxygenthan nitrogen is found in the layers.

By metal branch of the hysteresis the following is understood: if thecharacteristic at constant power and increasing oxygen flow is plottedagainst the generator data (current, voltage), the voltage increases upto a certain point, the breakover point. If the oxygen quantity isfurther increased, the voltage decreases markedly. The process hastipped over from metal mode into oxide mode. If the oxygen is againdecreased, a point is reached at which the process tips back again intometal mode. However, the two breakover points are not identical, ratherthe curve describes a hysteresis (cf. FIG. 1 of EP 0 795 890 A2).

The small quantities of nitrogen in the TiO₂ processes are not unusualper se and typical when using metallic targets for the processstabilization. When employing ceramic targets, the nitrogen can beomitted. It is probable that due to the higher pressure and the oxygenin the uppermost layer of Si₃N₄:O two parameters are available, whichpermit the setting of the barrier effect and/or of the internalmechanical layer stress conformed to the coating and the coatinginstallation.

This applies analogously also to the Si₃N₄ base layer (KT 1), however,here the increased sputter pressure does not yield any advantages.

With the continuous variation of oxygen flow and working pressure in thetwo Si₃N₄ processes (KT 1 or KT 7 and KT 8) variable parameters areavailable (thus virtual control levers) to conform the layer system tothe particular tempering process. A “tuning range” is consequentlyavailable in order to attain for the particular coating installation,glass quality and further processing (specifically the tempering) anoptimum conformation on the part of the coating.

The layer combination cited in the Table 1 before and after thetempering has the properties listed in the following Table 2. Herein thesymbols and abbreviations of the CIE LAB color system indicate thefollowing:

a*=color value on the red-green axis (dimensionless)

b*=color value on the yellow-blue axis (dimensionless)

Ty=transmission averaged in the visible range in percent

RGy=reflection averaged in the visible range from the glass side of thesample in percent

RFy=reflection averaged in the visible range from the layer side of thesample in percent

Haze=opacity or “milkinessD” (stray-light loss), stray-light componentin %

R/sq=surface resistivity in Ohm (cf. Hans Joachim Glaser:Duennfilmtechnologie auf Flachglas, pp. 134-137).

The thickness of the first Si₃N₄ layer is preferably 5 to 25 nm. Thesecond layer of TiO₂ has preferably also a thickness of 5 to 25 nm. Thethird layer, comprised of Ag, is preferably 8 to 18 nm thick. Thesucceeding layer of NiCrO_(k) is 3 to 8 nm thick. The last layer ofSi_(x)N_(y)O_(z) is preferably 25 to 65 nm thick.

TABLE 2 Before After Tempering Tempering Difference Ty 82.25 Ty 82.58 Ty1.33 a* −1.06 a* −1.63 a* −0.57 b* 1.93 b* 1.26 b* −0.67 RGy 9.95 RGy9.63 RGy −0.32 a* −1.99 a* −0.35 a* 1.64 b* −5.70 b* −4.78 b* 0.92 RFy6.43 RFy 6.95 RFy 0.52 a* −0.54 a* −0.82 a* 1.36 b* −5.36 b* −3.87 b*1.49 Haze 0.16 Haze 0.33 Haze 0.17 R/sq 4.80 R/sq 3.30 R/sq −1.50

Table 2 shows that there are only minimal differences in the essentialproperties of the coating before and after tempering. The tempering wascarried out at a temperature of approximately 620 to 700° C. Thesubstrate was therein heated for 2 to 20 minutes and subsequently cooledvery rapidly by means of compressed air.

Adhesive strength was tested by means of the so-called Erichsen WashTest according to ISO 11998. The results were faultless for all samples.The storage life was also tested, and specifically according to theso-called Storage Test for Resistance to Moisture according to DIN ENISO 6270 (DIN-50017). Here also only positive values were determined.

In addition, the transmission Ty is above 80%, the layer resistance isless than 5.0 Ohm/sq and for the colors in the reflection from the glassside applies—4<a*<0 as well as—7<b*<−2. The haze is less than 0.5%. Themechanical stability is robust, which could be determined by means of anErichsen Brush Test with 200 strokes.

1. A temperable substrate with a coating, comprising: a glass substrate;a first layer comprising Si_(x)N_(y)O_(z) disposed on the glasssubstrate; a second layer comprising TiO₂ disposed on the first layer; athird layer comprising Ag disposed on the second layer; a fourth layercomprising NiCrO_(k) disposed on the third layer; and a fifth layercomprising Si_(x)N_(y)O_(z) disposed on the fourth layer, whereinx/y≦0.75, y/z>4, and 0<k<2.
 2. The temperable substrate according toclaim 1, wherein the first layer is Si₃N₄.
 3. The temperable substrateaccording to claim 1, wherein the fifth layer is Si₃N₄.
 4. Thetemperable substrate according to claim 1, wherein the Si₃N₄ layers havean oxygen content O_(m), m being between 1 and 10⁻³.
 5. (canceled) 6.The temperable substrate according to claim 1, wherein the fourth layeris NiCr.
 7. The temperable substrate according to claim 1, wherein thefirst layer has a thickness of approximately 5 to 25 nm.
 8. Thetemperable substrate according to claim 1, wherein the second layer hasa thickness of approximately 5 to 25 nm.
 9. The temperable substrateaccording to claim 1, wherein the third layer has a thickness ofapproximately 8 to 18 nm.
 10. The temperable substrate according toclaim 1, wherein the fourth layer has a thickness of 3 to 8 nm.
 11. Thetemperable substrate according to claim 1, wherein the fifth layer has athickness of 25 to 65 nm.
 12. The temperable substrate according toclaim 7, wherein the first layer has a thickness of 15 nm.
 13. Thetemperable substrate according to claim 8, wherein the second layer hasa thickness of 15 nm.
 14. The temperable substrate according to claim 9,wherein the third layer has a thickness of 12.5 nm.
 15. The temperablesubstrate according to claim 10, wherein the fourth layer has athickness of 5 nm.
 16. The temperable substrate according to claim 11,wherein the fifth layer has a thickness of 40 to 50 nm.
 17. Thetemperable substrate according to claim 1, further comprising a layerfor setting the transmission that is disposed between the second layerand the third layer.
 18. The temperable substrate according to claim 17,wherein: the layer for setting the transmission istransmission-increasing; the layer for setting the transmissioncomprises ZnO; and the layer for setting the transmission comprised hasa thickness of 4 to 20 nm.
 19. The temperable substrate according toclaim 17, wherein: the layer for setting the transmission istransmission-increasing; the layer for setting the transmissioncomprises ZnO:Al; and the layer for setting the transmission comprisedhas a thickness of 5 to 10 nm.
 20. The temperable substrate according toclaim 17, wherein: the layer for setting the transmission istransmission-reducing; the layer for setting the transmission comprisesNiCr; and the layer for setting the transmission comprised has athickness of 1 to 10 nm.
 21. The temperable substrate according to claim17, wherein: the layer for setting the transmission istransmission-reducing; the layer for setting the transmission comprisesNiCrO; and the layer for setting the transmission comprised has athickness of 2 to 5 nm.
 22. A method for producing a temperablesubstrate with a coating comprising: sputtering a first layer comprisingSi_(x)N_(y)O_(z) on a glass substrate; sputtering a second layercomprising TiO₂ on the first layer; sputtering a third layer comprisingAg on the second layer; sputtering a fourth layer comprising NiCrO_(k)on the third layer; and sputtering a fifth layer comprisingSi_(x)N_(y)O_(z) on the fourth layer, wherein x/y≦0.75, y/z>4 and 0<k<2.23. The method according to claim 22, wherein the mechanical layerstress of the coating can be set by affecting the pressure and theoxygen flow in the production of the one of the Si_(x)N_(y)O_(z) layers.24. The method according to claim 22, wherein the working pressure inthe deposition of the fifth layer is in the range of 4.5×10⁻³ to 15×10⁻³mbar.
 25. The method according to claim 22, wherein the sputtering ofthe first and fifth layer further comprises supplying an oxygen quantitythat is smaller than the supplied nitrogen quantity.
 26. The methodaccording to claim 22, wherein in the production of the fifth layer theratio of N₂ to O₂ is greater than or equal to 4:1.